Sand consolidation by enzyme mediated calcium carbonate precipitation

ABSTRACT

Methods for treating a formation may include introducing components of a treatment solution into a wellbore such that the treatment solution contacts the formation to be treated, where the treatment solution may include urea, urease, a calcium ion source, one or more polysaccharides, a casein protein, a protease, an ionic compound, and a sugar, where the formation may have an amount of sand production before treatment and may be in fluid contact with the wellbore, and where an amount of sand production after treatment may be less than the amount of sand production before treatment. Consolidated sand structure compositions may include previously unconsolidated sand interlinked by inter-particle cementitious bonds comprising deposited calcium carbonate crystals, where the consolidated sand has a structural strength and the consolidated sand structure is porous to permit fluid flow through the composition.

BACKGROUND

Sand production from poorly consolidated formations, includingreservoirs, has been a persistent problem in the petroleum industry. Inparticular, production of sand from wells may cause a number ofproblems, such as slowing hydrocarbon production rate, scaling downholeequipment, including pipelines and valves, and damaging surfacefacilities. Furthermore, the repair or replacement of such equipment mayonly be performed during production shutdowns, where it is generallyundesirable to slow down producing assets.

SUMMARY

Certain embodiments of the disclosure will be described with referenceto the accompanying drawings, where like reference numerals denote likeelements. It should be understood, however, that the accompanyingfigures illustrate the various implementations described and are notmeant to limit the scope of various technologies described.

In one aspect, embodiments disclosed are directed to methods fortreating a formation. The methods may include introducing components ofa treatment solution into a wellbore such that the treatment solutioncontacts the formation to be treated. The treatment solution may includeurea, urease, a calcium ion source, one or more polysaccharides, acasein protein, a protease, an ionic compound, and a sugar. In themethods, the formation may have an amount of sand production beforetreatment and may be in fluid contact with the wellbore. Further, inthese methods, an amount of sand production after treatment may be lessthan the amount of sand production before treatment.

In another aspect, embodiments disclosed are directed to treatmentsolutions including a mixture of urea, urease, a calcium ion source, oneor more polysaccharides, a casein protein, a protease, an ioniccompound, and a sugar in an aqueous solution.

In another aspect, embodiments disclosed are directed to a consolidatedsand structure composition. The composition may include previouslyunconsolidated sand interlinked by inter-particle cementitious bondscomprising deposited calcium carbonate crystals. The consolidated sandhas a structural strength and the consolidated sand structure is porousto permit fluid flow through the composition.

Other aspects and advantages of this disclosure will be apparent fromthe following description made with reference to the accompanyingdrawings and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a representation of an arrangement of sand grains in aformation showing the cementation of the sand grains with urease-inducedcalcium carbonate precipitate.

FIGS. 2A-2C are Scanning Electron Microscopy (SEM) images at differentlevels of magnification of sand particles treated with an EICP (EnzymeInduced Carbonate Precipitation) solution without additives. FIGS. 2D-2Fare SEM images at different levels of magnification of sand particlestreated with an EICP solution comprising a combination of additives. Thelevels of magnification are from 100× to 2000×(140× in FIG. 2A, 1000× inFIG. 2B, 1400× in FIG. 2C, 100× in FIG. 2D, 1200× in FIG. 2E, and 2000×in FIG. 2F).

FIG. 3A is a graph showing the Energy Dispersive Spectroscopy (EDS)analysis of several regions at different levels of magnification asshown in FIGS. 2A-2C. FIG. 3B is a graph showing the EDS analysis ofseveral regions at different levels of magnification as shown in FIGS.2D-2F.

DETAILED DESCRIPTION

Several technologies have been used to reduce sand production, includinggravel packing and perforation methods. However, these techniquesrequire the use of heavy tools that add to the cost of a new well andongoing production. In addition, these techniques employ mechanicaltechnologies that unduly interfere with the workover and completionprocesses, which are continuously applied during the production life ofa wellbore.

Enzyme Induced Carbonate Precipitation (EICP) is a method of carbonateprecipitation via hydrolysis of urea employing urease enzyme. Carbonateprecipitation via hydrolysis of urea is a technique that has beeninvestigated to control sand production. This technique utilizes theurease enzyme to catalyze the hydrolysis of urea (ureolysis) in anaqueous solution, causing in the presence of calcium ions, the formationof carbonate ions leads to calcium carbonate precipitation.

EICP is an in situ chemical reaction that may be a useful part of amethod for effecting sand consolidation. EICP employs a urease enzyme tocatalyze the hydrolysis of urea in an aqueous solution. EICP in thepresence of divalent ions generates ammonium ions and a carbonatemineral that precipitates out of the aqueous solution. For example, inthe presence of calcium chloride (CaCl₂)), EICP results in calciumcarbonate (CaCO₃) precipitate as shown in Equation 1:

$\begin{matrix}{{H_{2}N} - {C0} - {NH}_{2} + {2H_{2}0} + {{{Ca}^{2 +}\overset{urease}{\Longleftrightarrow}2}{NH}_{4^{+}}} + {{{CaC0}_{3}(s)}.}} & \left( {{Equation}1} \right)\end{matrix}$

Mineral precipitation may include one or more cations that may produceone or several phases of carbonate minerals, including calcite.

However, it has been found that mere carbonate precipitation using EICPis not sufficient to form cementation via inter-particle bonding. Thecalcium carbonate precipitates as a fine powder that does not adhere toitself. Because it does not adhere to itself, the fine mineral particlesdo not provide cementation between sand particles. Withoutinter-particle bonding, such properties are not achieved.

Embodiments in accordance with the present disclosure generally relateto methods for reducing sand production from formations using EICP incombination with additives to produce consolidated sand particles. Inone or more embodiments, mineral precipitate may form cementationbridges and fill voids between sand particles. Use of an EICP solutionwith a combination of additives has been found to result in calciumcarbonate adhering to itself, thus providing cementation between sandparticles.

The application of the EICP technique using an EICP solution comprisinga combination of additives to consolidate sand particles and thereforereduce sand production is more effective than mechanical sand controltechnologies previously described. More particularly, the addition of acomposition of chemical compounds in an EIPC system has been found toresult in an environmentally-friendly and reversible sand controlsystem. In particular, the reversibility of such an EIPC systemalleviates the issue of potential plugging of reservoirs when usingsolutions based on resin mediated sand consolidation chemicals. If thepermeability is impacted by the enzymatic based solution during thechemical placement process, acid may be injected and some of the lostpermeability may be retained, because CaCO₃ is an acid soluble material.

The use of such a chemical composition in an EIPC system has also beenfound to consolidate sand particles and reduce sand production informations under typical hydrocarbon production conditions. Thistechnique is also more flexible in that it can be introduced into awellbore that has equipment in place. Mechanical techniques, aspreviously described, require significant downtime, loss of productionefficiency, and may cause safety and wellbore control issues fromremoving and replacing downhole equipment.

One or more embodiments of the present disclosure relate to an EICPtechnique that relies on the hydrolysis of urea by the enzyme urease inan aqueous solution, forming carbonic acid and ammonia. In the presenceof calcium ions in the solution, the carbonate ions precipitate ascalcium carbonate. The precipitating calcium carbonate from the aqueoussolution acts as the cementing agent. The cementing agent may aid inpreventing sand production at high temperature (for example, at least70° C.) in a formation. For the purposes of this disclosure, the term“high temperature” is referring to formation temperatures at or greaterthan about 70° C., such as in the range of 70° C. to 100° C. Theaddition of chemical additives to the aqueous solution comprising theEICP system improves the strength of the sand consolidation form.Chemical additives may include, but are not limited to, polysaccharides,such as naturally-derived gums, including guar gum and xanthan gum;proteins, for example, casein protein; sugars or sucrose derivatives,for example sucralose; an ionic compounds, such as sodium chloride; andan additional enzyme, such as protease. It has also been discovered thatthe functionality of the enzyme reaction may occur at reactiontemperatures conditions of about 70° C., for example, temperatures inthe range of 70° C. to 100° C.

One or more embodiments of the present disclosure relate to a method toreduce sand production from unconsolidated or poorly-consolidated hightemperature formations. In particular, the method includes introducingan aqueous treatment solution including urea, urease, a calcium ionsource, a polysaccharide, a casein protein, a sugar, an ionic compounds,and a protease. The method leads to a chemical reaction that can becarried out at temperatures greater than about 70° C., such as in therange of 70° C. to 100° C. The present method is a robust chemicaltechnology that can be used for plugging fractures, consolidating sand,such as from sandstone formations, and minimizing proppant flow back inhydraulic fracturing.

FIG. 1 is a representation of an arrangement of sand grains in aformation showing the cementation of the sand grains with urease-inducedcalcium carbonate precipitate. FIG. 1 illustrates an arrangement 100 ofsand grains 101 in a formation showing the cementation of the sandgrains 101 with urease-induced calcium carbonate precipitate 102. Asillustrated in FIG. 1 , the urease-induced calcium carbonate precipitate102 may act as a cementing agent for the sand grains 101, which arecemented through bridges of calcium carbonate crystallites. Thesebridges form a consolidated but still porous structure, where the flowof fluids (arrow 103) may pass through the 3D lattice structure. Such aconsolidated yet porous structure of calcium carbonate crystallitesresults from the use of an EICP solution comprising a combination ofadditives according to one or more embodiments of the presentdisclosure.

The addition of several chemicals (for example, guar gum, xanthan gum,casein protein, sodium chloride, sugar, and protease) to an aqueous EICPsolution comprising urea, urease, and a calcium ion source, may improvethe strength of sand consolidation. The increase in sand consolidationstrength even at high temperatures by adding the chemical composition tothe EICP solution may result from enzyme stabilization. Furthermore,proteins and guar gum may precipitate and act as chelating agents,reducing the precipitation rate and favoring the formation of largecalcite crystals. Additionally, such a chemical composition mayprecipitate and provide nucleation sites that favor calcite crystalformation. Accordingly, the method of contacting a formation with anaqueous solution, including, but not limited to, urea, urease, a calciumion source, a polysaccharide, such as xanthan gum or guar gum, a caseinprotein, an ionic compound, such as sodium chloride, a sugar, and aprotease, may provide for sand control.

One or more embodiments of the present disclosure relate to methods forreducing sand production from formations. The methods may includetreating the formations with an aqueous treatment solutions comprisingurea, urease, a calcium ion source, a polysaccharide, casein protein, anionic compound, such as sodium chloride, a sugar, and a protease.

One or more embodiments of the present disclosure relate to methods ofpreventing sand production in formations. The methods may includetreating the formations with an aqueous solutions comprising urea,urease, calcium ion source, a polysaccharide, casein protein, an ioniccompound, such as sodium chloride, a sugar, and a protease.

In one or more embodiments, the methods for reducing sand production andfor consolidating sand particles in high temperature formations mayinclude the cementation of sand particles, including silt particles,sediments, soil particles, rock particles, sandstone particles, shaleparticles, limestone particles, gypsum particles, dolostone particles,and clay particles.

In one or more embodiments, the methods for treating formations, such asby reducing sand production and for producing consolidated sandparticles, may comprise introducing into a wellbore an aqueous treatmentsolution comprising urea, urease, a calcium ion source, one or morepolysaccharides, a casein protein, a protease, an ionic compound, and asugar. The formations may comprise a plurality of sand particles suchthat the formations, being in fluid contact with the wellbore, have anamount of sand production before treatment. The treatment solution maycontact the formations to be treated so that the amount of sandproduction after treatment is less than the amount of sand productionbefore treatment.

In one or more embodiments, the treatment solution used in the methodsfor reducing sand production and for producing consolidated sandparticles in formations is an aqueous solution. The precipitationprocess takes advantage of the supply of carbonate ions derived fromurea hydrolysis and of an increase in pH generated by the reaction(formation of ammonia). The production of hydroxide ions from ammoniareaction in water brings about an increase in pH, which in turn leads tothe formation of carbonate ions.

The aqueous solution is a homogenous mixture of different additives. Inone or more embodiments, the an aqueous solution including urea. Urea isan organic compound of the chemical formula CO(NH₂)₂. Urea is acolorless, odorless, water soluble substance with low toxicity (LD₅₀=12g/kg (grams of substance per kilogram of body weight) for mouse, AgriumMaterial Safety Data Sheet (MSDS)). Any suitable source of urea may beused. In one or more embodiments, the urea may be present in thesolution at concentrations in a range of from about 0.5 M (moles perliter of aqueous solution) to about 1.5 M urea, such as from about 0.6 Mto about 1.4 M, or from about 0.7 M to about 1.3 M, or from about 0.8 Mto about 1.2 M.

In one or more embodiments, the aqueous solution may include the enzymeurease. The urease of the solution used in the methods for reducing sandproduction and for producing consolidated sand particles may besynthetically produced or obtained by extraction from any suitablesource, including but not limited to, bacteria, plants, invertebrates,and fungi. In one or more embodiments, a plant derived urease extractmay be used. In one or more embodiments, the solution may include ureaseat concentrations in a range of from about 1 g/L (gram per liter ofaqueous solution) to about 4 g/L, or from about 1.5 g/L to about 3.5g/L, or from about 2 g/L to about 3 g/L.

In one or more embodiments, the calcium ion source of the aqueoussolution may comprise calcium chloride, calcium nitrate, calciumnitrite, calcium sulfate, calcium acetate, calcium oxalate, and mixturesthereof. In addition, the calcium ion source may comprise any hydrate orsolvate form of the calcium ion. For example, the calcium ion source maycomprise calcium chloride dihydrate. In one or more embodiments, thecalcium ion source may be present in the aqueous solution atconcentrations in a range of from about 0.50 M to about 1.0 M, such asfrom about 0.55 M to about 0.95 M, or from about 0.60 M to about 0.90 M,or from about 0.65 M to about 0.85 M. Other calcium ion sources, such ascalcium nitrate, may be converted into calcium carbonate. Calciumchloride is a useful source of calcium ions.

In one or more embodiments, the polysaccharide of the aqueous solutionmay comprise xanthan gum. In one or more embodiments, the polysaccharidemay comprise a galactomannan polysaccharide, such as guar gum, atconcentrations in a range of from about 0.50 M to about 1.0 M.

In one or more embodiments, the casein protein of the aqueous solutionmay comprise a micellar casein protein. The solution may include caseinprotein at concentrations in a range of from about 2 g/L (gram per literof aqueous solution) to about 4 g/L.

In one or more embodiments, the aqueous solution may include one or moreionic compounds, such as sodium chloride. The solution may also includea sugar and sugar derivatives, such as sucrose derivatives, such assucralose. Furthermore, the solution may also include a protease, forexample, a protease that may be obtained from Aspergillus niger orAspergillus oryzae. Aminogen is a protein digesting enzyme (protease)that catalyzes the breakdown of proteins into smaller polypeptides oramino acids by breaking the peptide bonds between the amino acids.

One or more embodiments may include methods for treating a formation.For example, the methods may reduce sand production from the formation.The methods may include introducing a treatment solution into a wellboresuch that the treatment solution contacts the formation to be treated,where the treatment solution includes urea, urease, a calcium ionsource, a polysaccharide, and casein protein. The solution of urea,urease, a calcium ion source, one or more polysaccharides, a caseinprotein, a protease, an ionic compound, and a sugar. The formation hasan amount of sand production before treatment and is in fluid contactwith the wellbore and an amount of sand production after treatment isless than the amount of sand production before treatment.

In one or more embodiments, the treatment solution used in the methodsfor treating a formation by reducing sand production from the formationmay be prepared by mixing a first solution with a second solution priorto introducing the aqueous solution into the wellbore such that itcontacts the formation to be treated. In some other embodiments, thecomponents may be introduced separately as a first solution and a secondsolution or in various combinations and may be mixed in situ usingcoiled tubing, for example. The first solution may comprise urea, acalcium ion source, one or more polysaccharides, casein protein, aprotease, an ionic compound, and a sugar. The second solution maycomprise urease. In one or more embodiments, the first and secondsolutions may be mixed together and introduced into the wellbore to formthe treatment solution in the wellbore. The mixture may contact the sandparticles in the formation shortly after the mixing, whereinprecipitation of calcium carbonate takes place. The addition of achemical composition comprising casein, one or more polysaccharide(s),sodium chloride, sucralose, and protease, is believed to decrease thereaction rate and slows down the precipitation of calcium carbonate ascompared with a solution without the chemical composition. Although notwanting to be bound by theory, this is believed to allow the EICPtreatment solution to reach the formation before the calcium carbonateprecipitation sets inside the formation. The addition of the chemicalcombination to the EICP solution facilitates the formation of largercalcium carbonate crystals as compared to the EICP solution alonewithout the additional chemical combination from which small calcitecrystals form. The large calcite crystal formation is believed to occurdue to the slower rate of calcite precipitation from the embodimentaqueous solution than mere EICP solutions.

According to one or more embodiments, the treatment solution may beintroduced at a temperature that is less than the temperature of theformation. The methods for treating a formation may further includemaintaining the wellbore such that the treatment solution achieves atemperature in a range of from about 70° C. to 100° C. In the methodsfor treating a formation, the treatment solution may be introduced at atemperature less than the formation temperature, such as at temperaturesless than 100° C., or less than 70° C., allowing the calciteprecipitation to take place. The methods may further comprisemaintaining the treatment solution in the formation such that thesolution temperature rises to a temperature in a range of from about 70°C. to 100° C.

According to one or more embodiments, the methods for treating aformation may further include providing the components of the treatmentsolution, such that providing these components may include providing afirst solution and a second solution, where the first solution comprisesthe urea, the calcium ion source, the one or more polysaccharides, thecasein protein, the protease, the ionic compound, and the sugar, andwhere the second solution comprises the urease. The treatment solutionmay be provided in parts or it may be premixed with a thermal buffer orinhibitor.

According to one or more embodiments, in the methods for treating aformation, calcium carbonate crystals may crystallize on the surface ofthe sand particles of the formations. The calcium carbonate crystals mayhave a size in a range of from about 0.1 to about 0.5 μm (micrometer).The calcium carbonate also precipitated between formations particlesresulting in the formation of inter-particle contacts.

One or more embodiments may include methods of producing consolidatedsand particles in formations. The method may include introducing intothe wellbore an aqueous solution, the aqueous solution comprising urea,urease, a calcium ion source, a polysaccharide, and casein protein. Inthese methods, the temperature of the aqueous solution at the time ofcontacting may be at least about 70° C., for example, in a range of fromabout 70° C. to about 100° C. The consolidated sand particles of theformations may include calcium carbonate crystals. In one or moreembodiments, the calcium carbonate crystals may have a size in a rangeof from about 2 to about 6 μm.

In one or more embodiments, the consolidated sand particles of theformations treated by methods according to one or more embodiments mayinclude calcium carbonate crystals such that the consolidated materialdisintegrates upon applying a force, such as manual force. Sandparticles treated with embodiment solution formulations, including onlyurea, urease and a calcium source, resulted in a slurry of wet sand thatimmediately yields to any application of force and does not consolidate.

In one or more embodiments, the components of the aqueous solutions maybe introduced in a wellbore such that it contacts a formation.Introduction may include, but is not limited to, flushing, injecting,mixing, spraying, dripping, or trickling onto or into the formation.

In one or more embodiments, a consolidated sand structure compositionincludes previously unconsolidated sand interlinked by inter-particlecementitious bonds comprising deposited calcium carbonate crystals,where the consolidated sand has a structural strength, and where theconsolidated sand structure is porous to permit fluid flow through thecomposition. In one or more embodiments, the inter-particle cementitiousbonds of the consolidated sand structure composition may includedeposited calcium carbonate crystals form at a temperature in a range offrom about 70° C. to about 100° C. in the presence of a treatmentsolution. Such a treatment solution may include a mixture of urea,urease, a calcium ion source, one or more polysaccharides, a caseinprotein, a protease, an ionic compound, and a sugar in an aqueoussolution.

EXAMPLES

The following examples are merely illustrative and should not beinterpreted as limiting the scope of the present disclosure.

Example 1

EICP Formulations. EICP formulations were prepared by dissolving calciumchloride dihydrate, urea and urease enzyme and, in treatment cases, anda chemical composition, into distilled water. Two different EICPformulations were prepared for sand treatment.

EICP Formulation 1 (Comparative Solution) was prepared by dissolvingcalcium chloride dihydrate, urea, and urease enzyme in deionized water.EICP Formulation 1 was a solution composed of 1.0 M urea, 0.67 M calciumchloride, and 3 g/L urease enzyme.

EICP Formulation 2 (Treatment Solution) was prepared by preparing twoseparate solutions. A first solution was prepared by dissolving calciumchloride dihydrate, urea, and a chemical composition containing micellarcasein protein, xanthan gum, guar gum, sodium chloride, sucralose, andprotease AMINOGEN®, (USN; United Kingdom), in deionized water. A secondsolution was prepared by dissolving urease enzyme in deionized water.The two solutions were combined and mixed together to provide EICPFormulation 1. EICP Formulation 2 was composed of 1.0 M urea, 0.67 Mcalcium chloride, and 3 g/L urease enzyme, and 4 g/L of a chemicalcomposition containing micellar casein protein, xanthan gum, guar gum,sodium chloride, sucralose, and protease AMINOGEN®.

Sand treatment. Sand samples were treated with either EICP Formulation 1or EICP Formulation 2. Test specimens were prepared by mixing each sandsample with either EICP Formulation 1 or EICP Formulation 2 and byexposing each sample to different temperature conditions (70° C. to 100°C.). The increase in sand consolidation strength at these temperaturesby adding the chemical combination to the EICP solution may be due toenzyme stabilization. Furthermore, proteins and guar gum may precipitateand act as chelating agents, reducing the precipitation rate andfavoring the formation of large calcite crystals. Additionally, suchchemical combination may precipitate and provide nucleation sites thatfavor large calcite crystal formation at these temperatures.

A sample of sand particles treated with Formulation 1 resulted in a wetsandy mixture that did not have consolidation between the sandparticles. In contrast, the treatment of sand particles with Formulation2 resulted in a consolidated sand mixture that disintegrated upon theapplication of manual force. Similar results were observed at hightemperatures of 70° C. to 100° C.

Microscale Identifications. XRD (X-Ray Diffraction) analyses wereperformed on intact pieces of specimens from the sand samples treatedwith either EICP Formulation 1 or EICP Formulation 2 to identify thecrystal phase of calcium carbonate. SEM imaging was carried out on theseintact pieces to visualize the morphology of calcium carbonate.

FIGS. 2A-2C show the SEM images at different levels of magnificationperformed on intact pieces of specimens of sand particles treated withEICP Formulation 1. FIGS. 2D-2E show the SEM images at different levelsof magnification performed on intact pieces of specimens of sandparticles treated with EICP Formulation 2.

SEM imaging showed that treatment of sand particles with the comparativeexample (an EICP solution without the chemical composition) formed smallcalcite crystals cladding the sand particle surface. These calcitecrystals had sizes of about 0.5 to 1 μm. The region indicated by arrows201, 202, and 203, on FIGS. 2A-2C, respectively, shows the surfacecalcite at different levels of magnification. In contrast, theembodiment chemical composition comprising micellar casein protein,xanthan gum, guar gum, sodium chloride, sucralose, and proteaseAMINOGEN® to the EICP solution used for the sand particle treatmentresulted in the formation of an embodiment resultant with large calcitecrystals having sizes of about 2 to about 6 μm. Precipitation mainlyexhibited inter-particle contacts. The region indicated by arrows 206,207, and 208, on FIGS. 2D-2F, respectively, shows the inter-particlecontacts. The regions indicated by arrows 204 and 205 on FIG. 2D showsbroken inter-particle bonds. The large calcite crystals andinter-particle pattern of precipitation resulting from the treatmentwith Formulation 2 is believed to be a major contributor to the increaseof strength versus the comparative specimens treated without adding thechemical composition containing protein and polysaccharides to the EICPsolution.

As shown in FIGS. 3 a and 3 b , XRD testing confirmed precipitation ofcalcium carbonate in the calcite phase in of specimens of sand particlestreated with EICP Formulations 1 and 2. While the micellar caseinprotein, xanthan gum, guar gum, sodium chloride, sucralose, and proteaseincreased the cementation strength of sand particles through increasedinter-particle contacts, they did not change the crystalline structureof the calcium carbonate on and between the sand particles.

Accordingly, the addition of chemical additives (for example, guar gum,xanthan gum, and casein protein) increased sand consolidation strengthand expanded the application of methods using EICP solutions includingsuch chemical additives to the treatment of formations at hightemperature conditions.

While only a limited number of embodiments have been described, thoseskilled in the art having benefit of this disclosure will appreciatethat other embodiments can be devised which do not depart from the scopeof the disclosure.

Although the preceding description has been described here withreference to particular means, materials and embodiments, it is notintended to be limited to the particulars disclosed here; rather, itextends to all functionally equivalent structures, methods and uses,such as those within the scope of the appended claims.

The presently disclosed methods and compositions may suitably comprise,consist or consist essentially of the elements disclosed and may bepracticed in the absence of an element not disclosed. For example, thoseskilled in the art can recognize that certain steps can be combined intoa single step.

Unless defined otherwise, all technical and scientific terms used havethe same meaning as commonly understood by one of ordinary skill in theart to which these systems, apparatuses, methods, processes andcompositions belong.

The ranges of this disclosure may be expressed in the disclosure as fromabout one particular value, to about another particular value, or both.When such a range is expressed, it is to be understood that anotherembodiment is from the one particular value, to the other particularvalue, or both, along with all combinations within this range.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

As used here and in the appended claims, the words “comprise,” “has,”and “include” and all grammatical variations thereof are each intendedto have an open, non-limiting meaning that does not exclude additionalelements or steps.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, any means-plus-function clausesare intended to cover the structures described herein as performing therecited function(s) and equivalents of those structures. Similarly, anystep-plus-function clauses in the claims are intended to cover the actsdescribed here as performing the recited function(s) and equivalents ofthose acts. It is the express intention of the applicant not to invoke35 U.S.C. § 112(f) for any limitations of any of the claims herein,except for those in which the claim expressly uses the words “means for”or “step for” together with an associated function.

1.-14. (canceled)
 15. A treatment solution comprising a mixture of urea,urease, a calcium ion source, one or more polysaccharides, a caseinprotein, a protease, an ionic compound, and a sugar in an aqueoussolution.
 16. A consolidated sand structure composition, the compositioncomprising previously unconsolidated sand interlinked by inter-particlecementitious bonds comprising deposited calcium carbonate crystals,where the consolidated sand has a structural strength, and where theconsolidated sand structure is porous to permit fluid flow through thecomposition.
 17. The consolidated sand structure composition of claim16, where the inter-particle cementitious bonds comprising depositedcalcium carbonate crystals form at a temperature in a range of fromabout 70° C. to about 100° C. in the presence of a treatment solution.18. The consolidated sand structure composition of claim 17, where thetreatment solution comprises a mixture of urea, urease, a calcium ionsource, one or more polysaccharides, a casein protein, a protease, anionic compound, and a sugar in an aqueous solution.